1. Field of the Invention
The present invention relates to a cushion cell, the height of which can be changed by adjusting the pressure in a fluid chamber to cause the stretch of the cell, and to a cushion body such as a mattress using the cushion cell.
2. Description of the Related Art
Conventionally, as a cushion body that can prevent pressure gangrene (bedsore) and achieve excellent sleeping comfort and so forth due to the dispersion of body pressure, one with multiple cushion cells has been proposed, and application thereof to mattresses and other items is being studied. In other words, the cushion body is to be arranged on the bed surface and the like supporting the human body with a structure where a plurality of cushion cells each having a fluid chamber inside are provided and arranged in line. And, the human body support surface is configured by a collaborative action of multiple cushion bodies by having each cushion cell inflated with pressurized fluid supplied thereto. For example, the one disclosed in Japanese Patent No. JP-B-2615206 is such an item.
Meanwhile, since the cushion body is generally in an approximate shape of a cuboid, the disposition area of each cushion cell composing the cushion body is usually made into a square in plan. In a cushion body made of a plurality of cushion cells arranged in line, once a gap is created between cushion cells adjacent to each other, a problem occurs such as generation of bedsore and deterioration of touch feeling due to concentrated pressures of the human body. Therefore, if the disposition area is a square, it is desirable to make the top face of the cushion cell into a square corresponding to the disposition area.
However, in a deflated state of the cushion cell, if the top face thereof is made into a square form, the free length in the meridian direction varies along the circumferential direction around the central axis in inflating the cushion cell by pressurizing the fluid chamber so that stresses are focused on the side portion where the free length in the meridian direction is shorter to generate a constricted deformation with a depression along the outer periphery of the side. As a result, there was a risk of developing a problem of reduced durability of the cushion cell due to a concentrated action of stresses and unwanted gaps formed between the cushion cells adjacent to each other because of the constricted deformation.